Remove calls to `Einsum.init` #64

Job	Run time
Documentation	4m 7s
Examples Conda Py3	3m 30s
Tests for downstream project grudge	3m 36s
Pytest Firedrake	7m 41s
Tests for downstream project pytential	2m 43s
Examples Firedrake	4m 32s
Tests for downstream project mirgecom	3s
Flake8	15s
Tests for downstream project mirgecom_examples	3s
Mypy	3m 42s
Pylint	4m 8s
Pytest Conda Py3	6m 57s
	41m 17s

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